In cooling thermally highly loaded components of gas turbine engines often film cooling is applied. For film cooling, cooling fluid is guided onto a thermally loaded surface of a gas turbine component, such as for instance a blade, a vane, or a platform, and is intended to flow along this surface. Consequently, film cooling holes need to be inclined and diffuser shaped in order to provide a coolant layer directed along the component surface and to avoid separation of the coolant flow from the component surface.
It is known to produce such cooling holes e.g. by means of electrochemical methods or laser drilling. While the first production method is time consuming and expensive, laser drilling may result in significant heat intake which may have an impact on the metallurgical quality, and also in backstrikes on an opposite wall of e.g. a hollow blade or vane.
Likewise, drilling through thermal barrier coatings and a required dimensional accuracy as well as airflow capability may be an issue in manufacturing cooling holes.